A variety of intelligent hard disk drives have been developed, such as intelligent drive electronics (IDE) hard disk drives, small computer systems interface (SCSI) hard disk drives and fiber channel (FC) hard disk drives. In addition to the hard disk and associated drive electronics, an intelligent hard disk drive includes an integral controller designed specifically for the particular type of hard disk drive in order to control its operation.
In a computer, such as a personal computer, a hard disk drive is connected to the central processing unit by means of the system bus. In this regard, conventional computer architectures have a motherboard that includes a central processing unit and the system bus to which various peripherals, including a hard disk drive, are connected. To support the connection of the various peripherals, including a hard disk drive, to the system bus, a motherboard also generally includes a number of bus slots. A hard disk drive is typically connected to a respective bus slot by means of another bus designed specifically to support communications between the system bus and the hard disk drive. With respect to an IDE hard disk drive, for example, the IDE hard disk drive is connected to the respective bus slot by means of an advanced technology (AT) bus. An AT bus is a flat cable having 40 lines, each designed to support communication of a predetermined type of signal. For example, an AT bus includes a number of address lines, data lines, chip select lines, a reset line and others.
Although an intelligent hard disk drive includes an integral controller, most computers also include another controller disposed between the system bus and the bus extending to the hard disk drive for directing communications with the hard disk drive. In one embodiment depicted in FIG. 1, this controller is mounted upon the motherboard 10 so as to be in communication with both the system bus and the hard disk drive 12. For example, a portion of the bus that extends to the hard disk drive may extend from the controller to a connector 14 that is also mounted upon the motherboard. This bus may be completed by an appropriate cable 16 having connectors on the opposed ends for connection, at a first end, with the connector mounted upon the motherboard and, at the other end, to a connector carried by the hard disk drive. As such, communication between the hard disk drive, the central processing unit and other components of the computer system is supported by the transfer of signals between the controller onboard the motherboard and the hard disk drive.
In other configurations such as that depicted in FIG. 2, the controller is not mounted upon the motherboard 10, but is, instead, mounted upon a separate printed circuit board, termed the host controller board 18, designed to connect, typically by means of an edge connector, with one of the bus slots so as to communicate with the system bus. The host controller board includes the controller as well as related electronics. As described above in conjunction with the configuration in which the controller is mounted upon the motherboard, a portion of the bus that extends to the hard disk drive is also carried by this additional board and extends from the controller to a connector 20 mounted upon the host controller board. Again, a cable 16 having appropriate connectors on the opposed ends is mated at one end to the connector carried by the host controller board and, at the other end, to a connector carried by the hard disk drive 12 in order to establish communications therebetween. In either configuration in which the controller is mounted upon the motherboard or the host controller board, the controller and its associated electronics are typically termed the host and are designed to communicate directly with the hard disk drive as shown schematically in FIG. 3.
Of the intelligent hard disk drives, SCSI hard disk drives and FC hard disk drives are designed and specified to be hot swappable. In this regard, SCSI and FC hard disk drives may be removed, inserted and/or exchanged while the computer is operating and power is supplied to the various peripherals, including other disk drives. In contrast, IDE hard disk drives have not traditionally been hot swappable. Instead, IDE hard disk drives have historically only been able to be removed, inserted or otherwise exchanged while the computer was shut down or powered off. In addition, SCSI and FC hard disk drives are designed to provide various status signals indicative of, among other things, the operational state of the hard disk drive to the host. Unfortunately, IDE hard disk drives do not include provisions for transmitting similar status signals to the host.
For various reasons, SCSI hard disk drives are typically utilized by mid-range and high-end computers and FC hard disk drives are used nearly exclusively in high-end computers. In contrast, IDE hard disk drives are not generally included in higher-end systems. Even though IDE hard disk drives are traditionally utilized in low-end systems, it would still be advantageous for the IDE hard disk drives to be hot swappable and to be capable of providing status or other signals to the host.